1. Field of the Invention
The present invention relates to a heat exchanger tube preferably used for a heat exchanger tube for a cooling medium or the like which constitutes a condenser of an air conditioner or a refrigerator.
This application is based on Japanese Patent Application No. 2000-13400, the contents of which are incorporated herein by reference.
2. Discussion of Background
In a cooling device such as an air conditioner or a refrigerator or the like, a cooling medium (fluid) of Freon or the like is first compressed to form a high temperature and high pressure gas and is then liquefied by cooling the gas with a condenser. In the condenser is incorporated a heat exchanger tube through which a cooling medium flows, and a high temperature and high pressure gaseous cooling medium is gradually cooled by heat dissipation while passing through the tube so that it is condensed into a liquid. As this kind of heat exchanger tubes, a heat exchanger tube shown in FIG. 10 or the like has been known. A tube body 7 is constituted by a solder material-cladded band-shaped metallic plate member 1 being folded or bent with a fold 2 in a direction of its extension, connecting end portions 5, 5, which are mutually brought into contact with end portions of one wall portion 3 and the other wall portion 4 folded and extended in the same direction, are formed and are welded thereto, and a cooling medium passage 6 is formed between these wall portions.
Further, the curvature radius of the fold 2 is smaller than the width of the wall portion 3 or 4, and the distance between the wall portions 3 and 4 is smaller than the width of the wall portion 3 or 4. This shape is defined to reduce the time required for heat dissipation by decreasing the distance from the center of the tube body 7 to the wall portion.
The thus formed interior defines a cooling medium passage 6. A plurality of bulging wall portions 8, 8 . . . bulging in a bowl shape toward a direction of the opposite wall portions are formed on both opposite wall portions 3 and 4 of the tube body 7 in which the inner surface and the outer surface are defined as the heat entrance and exit surfaces for the cooling medium, and bulging leading ends of the bulging wall portions 8, 8 . . . are defined as connecting portions 9, 9 . . . The connecting portions 9, 9 . . . are brought into contact with opposite bulging wall portions in a plane and are welded by soldering. A cooling medium that flows in the interior of the tube is caused to generate a turbulent flow by these bulging wall portions 8, 8 . . . and is uniformly agitated within the tube body so that the temperature distribution of a fluid in a plane vertical to the flow is made uniform. Further, the opposite wall portions 3 and 4 are connected to each other by the plurality of welded bulging wall portions 8, 8 . . . and are supported against a pressure applied to the wall portions 3 and 4 of the flat tube body 7 when a high pressure cooling medium flows in the tube, thereby enhancing the pressure resistance of the tube body 7.
However, the above-mentioned conventional heat exchanger tube has the following problems.
Since the tube body is formed by folding a band-shaped metallic plate member with a fold, it tends to be deformed by an effect of the spring back at the fold, that is, the restoration of the bent portions, in such a manner that the opposite wall portions are separated from each other.
On the other hand, the opposite cooling medium agitating bulging portions bulging in bowl shapes are soldered in a plane at the connecting portions brought into contact with each other. However, when an oxide film formed on the surface of a solder material has been separated for soldering with flux, the bulging portion has a structure making discharge of the separated oxide film from the outer periphery of the surface-shaped connecting portion difficult. Thus, it is actually difficult to solder at the center of the connecting portion.
Therefore, in addition to the circumstances of difficult soldering, when a force which separates the opposite wall portions by the spring back is applied to the tube body, firm welding is not performed at the connecting portion between the bulging wall portion leading ends. As a result, the tube body has no support against the pressure of the cooling medium, whereby the pressure resistance of the tube body deteriorates.
The present invention was made in consideration of the above-mentioned circumstances. The object of the present invention is to provide a heat exchanger tube having an improved soldering process and high pressure resistance by forming a structure which easily discharges an oxide film separated with flux, and prevents the deformation of the tube body due to the spring back effect.
A first aspect of the invention relates to a heat exchanger tube having the tube body whose interior is defined as a passage of a fluid and whose inner and outer surfaces are defined as heat entrance and exit surfaces of the fluid and is characterized in that a bulging wall portion bulging toward a direction of opposite wall portions is formed on one or both of the opposite wall portions of said tube body, the bulging leading ends of said bulging wall portions are defined as connecting portions linearly protruding and said connecting portions are linearly brought into contact with the opposite wall portions and are fixed thereto.
By providing such a configuration, a soldering material oxide separated with flux at the connecting portion of the leading end of the bulging wall portion flows out of a linear connecting portion whereby soldering is improved and the opposite wall portions are firmly soldered without occurrence of a weld failure.
A second aspect of the invention relates to a heat exchanger tube, and is characterized in that it provides a first bulging wall portion bulging in a bowl shape in a direction of wall portions opposite to said bulging wall portion, with a plurality of said first bulging wall portions being formed on said tube body.
By providing such a configuration, the opposite wall portions are connected to each other at a plurality of positions by a plurality of first bulging wall portions. Further, a fluid flowing in the interior of the tube generates a turbulence flow with the plurality of first bulging wall portions and is uniformly agitated in the tube body.
A third aspect of the invention relates to a heat exchanger tube, and is characterized in that a plurality of protrusions with triangular sections protruding linearly in the direction of the extension of the tube body are formed on the inner surface of said tube body in such a manner that they are adjacent to each other, said protrusions being defined as said connecting portions.
By providing such a configuration, positions which are linearly soldered are increased at the connecting portions of the leading ends of the first bulging wall portions where opposite wall portions are connected to each other. Thus, the opposite wall portions are firmly connected to each other.
Further, since the surface area of the inner surface of the tube body defined as the heat entrance or exit surface is increased, a contact area with the fluid is increased.
A fourth aspect of the invention relates to a heat exchanger tube, and is characterized in that it provides a second bulging wall portion including a first extending portion extending toward the direction of wall portions opposite from one reference position of the wall portion to serve as said bulging wall portion, a return portion which is folded back from said first extending portion to the direction of said reference position and a second extending portion which is folded back from the return portion to said one reference position of the wall portion.
By providing such a configuration the folded portion of the second bulging wall portion and the opposite wall portions are linearly brought into contact with each other in a direction of the extension of the tube body, a soldering length is increased and the soldering material oxide separated from flux speedily flows out of the linear connecting portion whereby soldering can be improved. Thus, the opposite wall portions are firmly connected to each other.
A fifth aspect of the invention relates to a heat exchanger tube, and is characterized in that said tube body is formed by a band-shaped plate member extending in one direction, said plate member is defined as said one wall portion in the intermediate portion of the plate member in the width direction and is folded with two folds in a direction of the extension of the tube body in both end portions of said one wall portion, said folded portions are extended to each other in an adjacent direction to form the other wall portion, said folded portion is further folded in a direction of said one wall portion at a contact position and is extended toward the same direction of said one wall portion to form a third extending portion, the end portion of said third extending portion being brought into contact with said other wall portion and being fixed thereto.
By providing such a configuration the end portion of the third bulging wall portion and the other wall portion are linearly brought into contact with each other in a direction of the extension of the tube body, the soldering length is increased, and the soldering material oxide separated from flux speedily flows out of the linear connecting portion whereby soldering can be improved. Thus, the opposite wall portions are firmly connected to each other.
Further, since the weld surface in the third extending portion composed of a mutual contact portion is pressed from both sides by the pressure of a fluid flowing in the passage to be press bonded, the pressure resistance is enhanced.
A sixth aspect of the invention relates to a heat exchanger tube, and is characterized in that an opening portion for allowing the fluid passages partitioned with said third extending portion to communicate with each other is formed in said third extending portion.
By providing such a configuration a fluid flowing through the tube body is passed between the passages of a fluid divided with the third extending portion, whereby it flows through the entire interior of the tube body.
A seventh aspect of the invention relates to a heat exchanger tube, and is characterized in that said tube body comprises a pair of plate members extending in the direction of the extension of said tube body, the plate members are formed so that the passage for said fluid is formed between the plate members, and the plate members have connected end portions overhanging on each side, on both respective end portions, the respective connected end portions of these plate members being brought into contact with each other and being fixed thereto.
By providing such a configuration, both the wall portions of the tube body are formed with a pair of band-shaped plate members. Thus, to form both wall portions it is not necessary to fold a band-shaped plate member by 180 degrees with a fold in a direction of the extension of the plate member. The spring back is increased with the magnitude of the bending angle. Accordingly, a bending angle required for forming the tube body is decreased and a force which acts on the wall portion by the spring back is decreased.
A eighth aspect of the invention relates to a heat exchanger tube, and is characterized in that said connecting end portion is fastened with a U-shaped folded fastening plate member.
By providing such a configuration the connecting portions which are brought into contact with each other in a plane and are soldered therewith are externally reinforced with a fastening plate member, and a force due to the spring back applied to the weld surface or a force due to the fluid pressure is reduced.
A ninth aspect of the invention relates to a heat exchanger tube having the tube body whose interior is defined as a passage for a fluid and whose inner and outer surfaces are defined as heat entrance and exit surfaces for the fluid and is characterized in that in said tube body a band-shaped plate member is folded with a fold in the direction of the extension of the plate member, a passage of said fluid is formed between one wall portion and the other wall portion extending in the same direction by the folding, a plurality of spring back preventing portions where said one and the other wall portions are brought into contact with each other and are fixed in said folded portion is formed, connecting end portions brought into contact with each other are formed on the end portions of said one and the other wall portions, and said connecting end portions are fixed.
By providing such a configuration a force which causes the tube body to deform by the spring back is locally acted on the spring back preventing portion and the magnitude of the force of separating opposite wall portions is reduced.